15min:

B. OSTOJIC´, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Studentski trg 14-16, 11 000 Belgrade, Serbia; P. R. BUNKER, P. SCHWERDTFEGER, Centre for Theoretical Chemistry and Physics (CTCP), The New Zealand Institute for Advanced Study(NZIAS), Massey University Auckland, Private Bag 102904, North Shore City, 0745 Auckland, New Zealand; ARTUR GERTYCH, PER JENSEN, FB C -- Physikalische und Theoretische Chemie, Bergische Universität, D-42097 Wuppertal, Germany.

This study of CaOCa is the third in a series by us on Group 2 alkaline-earth M₂O hypermetallic oxides. As with our previous calculations in the series, on BeOBe and MgOMg, the ab initio calculations we report here show that CaOCa has a linear ¹ _g⁺ ground electronic state and a very low lying linear a ³ _u⁺ first excited triplet electronic state. For CaOCa we determine that the singlet-triplet splitting T _e( ) = 386 cm^-1. We calculate the three-dimensional potential energy surface, and the electric dipole moment surfaces, of each of the two states using a multireference configuration interaction (MRCISD) approach in combination with internally contracted multireference perturbation theory (RS2C) based on full-valence complete active space self-consistent field (FV-CASSCF) wavefunctions with a cc-pwCVQZ-DK basis set for Ca and a cc-pCVQZ basis set for O. We simulate the infrared absorption spectra of ⁴⁰Ca¹⁶O⁴⁰Ca in each of these electronic states in order to aid in its eventual spectroscopic characterization.